Ultrasonic cleaner

ABSTRACT

An electromechanical device is provided for cleaning small items by agitating a liquid at ultrasonic frequency. The desired ultrasonic vibrations are produced by a piezoelectric crystal operating in its radial mode wherein the crystal and a receptacle for receipt of the item to be cleaned are floatingly mounted between two gaskets in resilient compression.

0 United States Patent 1 1 3,595,5 32

[72] Inventors Edward ,1. Doyle 2,875,989 3/1959 Toulmin 259/D1G. 41 l'latboro; 3,026,093 3/1962 Haan et a1 134/1 X Ray ll. Enders, Columbia, bothoi, Pa. 3,056,589 10/1962 Daniel 259/DlG. 44 [21] Appl. No. 798,707 3,113,761 12/1963 Platzman. 134/184 X [22] Filed Feb. 12, 1969 3,301,535 1/1967 Brown 259/D1G. 44 [45] Patented July 27, 1971 3,445,092 5/1969 Fierle et a1 .4 134/184 X [73] Assignee Shick Electric nc. 3,464,672 9/1969 Massa 259/2 X Lancaster Primary Examiner-Walter A. Scheel Assistant Examiner-Alan l. Cantor 54] ULTRASOMC CLEANER Attorney-Kane, Dalsimer, Kane, Sullivan and Kurucz 4 Claims, 3 Drawing Figs.

[52] US. Cl 259/72, 259/D1G. 41 68/3 SS Int. Cl 7 B01 An electromechanical devige is provided for of Search cleaning small items agitating a at ultrasonic f 'equen- 44, [316- f 72; 68/3 55; 15/94; 134/154, 1 cy. The desired ultrasonic vibrations are produced by a piezoelectric crystal operating in its radial mode wherein the F Rderenm cued crystal and a receptacle for receipt of the item to be cleaned UNITED STATES PATENTS are floatingly mounted between two gaskets in resilient com- 2,81S,193 12/1957 Brown 259/72 pression.

r- I y i II u rc H I l 1 I n l l l ULTRASONIC CLEANER BACKGROUND OF THE INVENTION Heretofore, ultrasonic cleaning devices have been extensively used in laboratory and industrial applications but have not been practical for home use because of their relatively high cost and large size. The use of a piezoelectric crystal as a source of vibratory energy and improved manufacturing techniques have enabled the design and production of an ultrasonic cleaner for home use. The proposed cleaner serves to provide a mechanical vibratory energy to a cleaning solution in which the object to be cleaned is submerged which, together with the wetting action of the cleaning solution, serves to dislodge and remove soil from the object.

One of the principal problems encountered in the design of ultrasonic cleaners is associated with the means for mounting the receptacle in which the cleaning action is to occur to the source of vibratory energy. In this regard, the receptacle must be physically and electrically isolated from the energy source but in such a manner as to avoid damping the vibratory energy source which should vibrate at or near its resonant frequency.

SUMMARY OF THE INVENTION It is, therefore, the principal object of the present invention to provide an improved ultrasonic cleaner that includes a piezoelectric crystal operating in its radial mode as the source of ultrasonic vibrations.

A further object is to provide means for mounting the clean ing receptacle to an associated housing in such a fashion as to enable the crystal to vibrate at substantially its resonant frequency with a minimum of energy loss due to damping while, at the same time, providing suitable insulation between the cleaning receptacle and the piezoelectric crystal to prevent electrical leakage between the relatively high voltage associated with the crystal and the liquid in the receptacle and to afford a watertight seal between the receptacle and the housing.

These and other beneficial objects and advantages are at-' tained in accordance with the present invention by providing an ultrasonic cleaner which includes a base structure, a housing mounted to the base structure and a cleaning receptacle supported by a resilient compression mounting between the base and housing. A piezoelectric crystal, designed to operate in its radial mode, is secured to the bottom of the receptacle and the associated electrical circuitry to excite the crystal is contained in the base.

The compression mounting includes a first rubber gasket disposed between the upper peripheral edge of the receptacle and the cleaner housing and a second rubber gasket disposed between the piezoelectric crystal and base. The durometer index of each of the gaskets is such as to avoid damping the receptacle during periods of excitation of the crystal. In this regard, the gaskets must be sufficiently resilient to permit free movement of the receptacle without enabling the receptacle to bottom against the housing or base. Also, the gaskets serve to provide a watertight seal between the receptacle and the housing and also to prevent electrical leakage between the crystal and the liquid in the receptacle.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a perspective view of an ultrasonic cleaner in accordance with the present invention;

FIG. 2 is a side elevational sectional view taken along reference line 2-2 in the direction of the arrows in FIG. 1; and

FIG. 3 is a schematic drawing of the electric circuitry associated with the ultrasonic cleaner of the present invention.

The present invention is illustrated in the accompanying figures wherein similar components are indicated by the same reference numeral throughout the several views. Reference is now made to FIG. 1, in particular, wherein the cleaner is depicted as comprising two connected, generally rectangular main portions, base 12, and housing 14. Both the base and housing are formed of a suitable material such as molded polystyrene thermoplastic. Base 12 includes a name plate 16 mounted on its front side. An on-of control switch 18 and indicating lamp 20 are mounted to name plate 16.

The housing 14 comprises a generally rectangular elongated sleeve. The lower portion of housing 14 is in the form of a depending skirt 24, the bottom edge 26 of which is spaced somewhat above the upper peripheral ledge 28 of base 12. An inwardly and downwardly directed circumferential bead 29 extends from the inner surfaces of housing 14.

Within skirt 24 of housing 14, a receptacle tank 30 is pro vided which serves to receive the liquid cleaning solution and object to be cleaned. Tank 30 may be formed of stainless steel for most purposes or, for low energy applications, may be formed of a suitable plastic material. Affixed to the bottom of tank 30 is a piezoelectric crystal 32 which is adapted to provide the desired vibratory energy to tank 30. In this regard, the crystal 32 is adhesively bonded to one face of a sheet of electrical insulating material 34 and the opposite face of sheet 34 is adhesively bonded to the bottom of tank 30.

The tank 30 and bonded crystal 32 are held in position within housing 14 by a compression mounting which includes upper and lower resilient rubber gaskets 34 and 36, respectively. In this regard, the upper gasket 34 is interposed between the outwardly turned upper peripheral edge 38 of tank 30 and the bottom edge of bead 29. The lower gasket 36 supports the bottom of crystal 32 and it in turn rests on shoulder 40 of base 12. The housing 14 and base 12 are securely joined by fasteners 22 in such a manner that the gaskets 34 and 36 will be in compression as they hold the tank in position. The gaskets 34 and 36 serve to effectively isolate the tank 30 and crystal 32 from the housing 14 and base 12 and also serve to provide a watertight seal between the interior of the tank and the interior of base 12 where the electrical circuitry is contained. Thus, the possibility of liquid leakage or electrical leakage between the high voltage of crystal 32 and the liquid in tank 30 is prevented.

Base 12 is a generally hollow member, the interior of which contains the electrical circuitry associated with the piezoelectric crystal 32. In this regard, a chassis 42 is mounted to bottom plate 44 by fasteners 46. Suitable insulating rings 48 serve to isolate the chassis 42 from the bottom plate 44. The bottom plate 44, in turn, is fastened to base 12 by screws 50 which engage suitable slots 52 in the base. The base 12 is supported upon an underlying surface by supports 53 which are also held 7 in position by the bottom plate securing screws 50. Chassis 42 is an L-shaped metal member and the upwardly extending portion is used as a transistor heat sink and to mount the various electrical components.

Reference is now briefly made to FIG. 3 wherein a simplified schematic drawing of a typical circuitry that may be associated with the ultrasonic cleaner of the present invention is depicted. Thus, the cleaner is adapted to operate on a nominal IZO-volt AC power supply across its input terminals 56 and 58. The power cord that connects the cleaner to its power source may be either attached permanently to the device or it may be connected by a plug arrangement, thereby making the cord removable. An on-off switch 18 and indicating light 20 which are physically mounted to the front panel 16 of the cleaner are provided across the power input line. A diode rectifier 60 serves to rectify the AC input to the cleaner. The output of diode 60 is fed through a current-limiting resistor 62 whose value depends upon the amount of power desired for the piezoelectric crystal 64. The output of resistor 62 represents the DC or BrF input to the crystal control circuitry.

Resistors 66 and 68 are shunted across the 8+ and B terminals of the circuit and serve as a voltage divider'to forward bias the base of transistor 70 so that it will conduct when a voltage appears between its collector and emitter terminals. An induction coil 72, the inductance of which is such as to cause it to resonate electrically at the mechanical resonant frequency of the crystal 64 is provided between the collector of transistor 70 and one lead of capacitor 74. The other lead of capacitor 74 is coupled to the base of transistor 70. A second capacitor 76 which serves to bring the system to resonance is shunted across coil 72. Both the coil 72 and capacitor 76 may be either fixed or variable thus permitting variation in the resonant frequency to be attained. Coil 72 has a tap 78 that connects to the 3-!- supply and current travels from tap 78 through part 'of the coil winding 79, thereby placing a charge on the plus side of crystal 64 whose negative side is connected to the B- of the DC power source. During the initial onrush of current through coil 72, as described above, a current is induced in the remaining windings 80 of coil 72, thereby causing a current flow across capacitor 74 which will remove the forward bias from transistor 70, thereby rendering the same nonconducting. After crystal 64 has charged and current stops flowing, the reverse bias to the transistor base is diminished and the forward bias from the tap between resistors 66 and 68 causes transistor 70 to conduct, thereby discharging crystal 64 Current will then again flow through inductor 72, and the process repeats itself causing the crystal to vibrate at its resonant frequency. Diode 82 extending between the transistor base and ground is used to protect the base of transistor 70.

Thus, among others, the several objects of the invention, as specifically aforenoted, have been achieved.

Having thus described my invention, what I claim is:

1. An ultrasonic cleaning device including in combination a base structure, a housing supported on said base structure and fastened thereto, an inwardly projecting shoulder of said structure, a first resilient gasket on said shoulder, a piezoelectric crystal supported by said gasket, insulation means for-said crystal disposed on the upper surface thereof, a container resting upon said insulation means and supported by said crystal, a portion of said container, a second resilient gasket between said portion and said housing whereby said container is resiliently supported between said housing and said base.

2. An ultrasonic cleaning device in accordance with claim 1 in which said first gasket rests on said shoulder and supports said crystal on its edge and said second gasket is disposed between the upper peripheral edge of said container and the housing.

3. An ultrasonic cleaning device in accordance with claim 2 in which said housing and base are fastened so as to maintain said gaskets in resilient compression.

4. An ultrasonic cleaning device in accordance with claim 3 5 in which said first gasket contacting said shoulder and said 

1. An ultrasonic cleaning device including in combination a base structure, a housing supported on said base structure and fastened thereto, an inwardly projecting shoulder of said structure, a first resilient gasket on said shoulder, a piezoelectric crystal supported by said gasket, insulation means for said crystal disposed on the upper surface thereof, a container resting upon said insulation means and supported by said crystal, a portion of said container, a second resilient gasket between said portion and said housing whereby said container is resiliently supported between said housing and said base.
 2. An ultrasonic cleaning device in accordance with claim 1 in which said first gasket rests on said shoulder and supports said crystal on its edge and said second gasket is disposed between the upper peripheral edge of said container and the housing.
 3. An ultrasonic cleaning device in accordance with claim 2 in which said housing and base are fastened so as to maintain said gaskets iN resilient compression.
 4. An ultrasonic cleaning device in accordance with claim 3 in which said first gasket contacting said shoulder and said second gasket contacting said housing provide respective first and second watertight seals. 